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NITRATION WITH NITRATING MIXTURES

TABLE 18

149

Mixture of acids

Nitric acid

Sulphuric acid

Water

Specific heat

Cal/g

0.47

0.61

0.36

1.0

Enthalpy

at 0°C

kcal/kg

-54.8

-44.9

-24.4

0

Enthalpy Enthalpy

at 24°C at 35°C

kcal/kg kcal/kg

• -. 38.3
  -30.5 -
  -15.9 -
  +24 -

Thus, for the 100 kg mixture the enthalpies of the components at 24°C are:

nitric acid -30.5 x 30 = - 915.0 kcal

sulphuric acid -15.9x65.3 = -1038.3 kcal

water +24 x 4.7 = + 112.8 kcal

The total enthalpy of the components at 24°C is -1840.5 kcal. The enthalpy of 100 kg of
the mixture of acids at 35°C is
-38.3x100 = -3830 kcal
Hence the heat which must be removed during the preparation of 100 kg of the mixture so
as to maintain 35°C is
3830-1840.5 = 1989.5 kcal or 19.9 kcal/kg

Fro. 23.Heats of dilution of nitric acid, sulphuric acid,

mixtures (Rhodes and Nelson [4]).

HEATS OF DILUTION

and their

Heats of dilution at 18°C of mixed acid containing various known percentages

of sulphuric acid, nitric acid, and water were given in Table 16 (p. 144).

The data are presented graphically in Fig. 23. Thus for a mixed acid containing